Mover stabilizing and stator cooling arrangement of a 3-phase linear motor of a submersible oil pump

ABSTRACT

A mover stabilizing and stator cooling arrangement includes an upper sleeve surrounding the mover of the linear motor, a lower sleeve, a thermoconducting sleeve surrounding the stator and axially connected between the upper sleeve and the lower sleeve. The arrangement further includes a thermal grease filled in the space defined between the upper sleeve and the mover, the space defined between the thermoconducting sleeve and the stator, and the space defined between the lower sleeve and the outer tube for quick dissipation of waste heat. A stabilizer ring is set between the upper sleeve and the mover to stabilize axial movement of the mover. A piston and multiple one-way valve sets are mounted in the space between the lower sleeve and the outer tube for allowing adjustment of the volume in the thermoconducting sleeve responsive to expansion/contraction of the thermal grease due to temperature changes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a crude oil production system and morespecifically, to a mover stabilizing and stator cooling arrangement usedin a 3-phase linear motor of a submersible oil pump to stabilizereciprocating movement of the mover and to dissipate heat from thestator during operation of the motor.

2. Description of the Related Art

The best way to dissipate heat during operation of a motor is theutilization of natural air convection. Electric fan may be used toprovide forced air, enhancing heat dissipation.

U.S. Pat. No. 7,316,270 discloses an oil pumping unit using asubmersible oil pump driven by a synchronizing three-phase linear motor.According to this design, the oil pumping unit comprises a motor 10 anda pump 20. The motor 10 comprises a casing 13, a stator 12, and a mover11. The mover 11 comprises a center tube 14. The pump 20 comprises abarrel 23, a suction pipe 21, an upper chamber 25, a piston 26, and alower chamber 27. The suction pipe 21 is connected to the mover 11 forsynchronous reciprocation to suck in a fluid from the oil well.

According to this design, natural air or forced air cannot reach theinside of the linear motor 10 to dissipate heat from the linear motor10. When the pump is pumping the fluid, the running fluid passingthrough the center tube 14 carries heat away from the mover 11. However,the air gap between the mover 11 and the stator 12 does not transferheat easily, therefore heat tends to be accumulated at the stator 12.Further, the mover 11 of the linear motor 10 is relatively quite long,therefore off axial motion can easily happen during its reciprocatingmotion. An improvement is necessary to facilitate heat dissipation ofthe stator 12 and to stabilize the axial reciprocating motion of themover 11.

SUMMARY OF THE INVENTION

It is one object of the present invention to provide a mover stabilizingand stator cooling arrangement, which is practical for use in 3-phaselinear motor of a submersible oil pump to effectively stabilizing axialreciprocating motion of the mover of the linear motor and to efficientlydissipate heat from the stator during operation of the linear motor.

To achieve this and other objects of the present invention, the moverstabilizing and stator cooling arrangement is used in a 3-phase linearmotor of a submersible oil pump, comprising an upper sleeveconcentrically surrounding the mover of the linear motor, a lowersleeve, a thermoconducting sleeve concentrically surrounding the statorand axially connected between the upper sleeve and the lower sleeve, athermal grease filled in the space defined between the upper sleeve andthe mover and the space defined between the thermoconducting sleeve andthe stator and the space defined between the lower sleeve and the outertube for quick heat dissipation, and a stabilizer ring set between theupper sleeve and the mover to stabilize axial movement of the mover.

Further, a piston and multiple one-way valve sets mounted in the spacedefined between the lower sleeve and the outer tube for allowingadjustment of the volume in the thermoconducting sleeve subject toexpansion/contraction of the thermal grease during temperature change.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view, showing a down-stroke oil pumpingaction of a 3-phase linear motor-driven submersible oil pump of a crudeoil production system according to the prior art.

FIG. 2 corresponds to FIG. 1, showing an up-stroke oil pumping action ofthe 3-phase linear motor-driven submersible oil pump of the crude oilproduction system according to the prior art.

FIG. 3 is a schematic sectional view, showing a down-stroke oil pumpingaction of a 3-phase linear motor-driven submersible oil pump of a crudeoil production system according to the present invention.

FIG. 4 corresponds to FIG. 3, showing an up-stroke oil pumping action ofthe 3-phase linear motor-driven submersible oil pump of the crude oilproduction system according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 3, a linear motor 30 is shown comprised of a mover 31,a stator 32, and a casing 33. The mover 31 is movable up and down in thestator 32. The mover 31 comprises a center tube 34. A pump 40 is showncomprised of a suction tube 41, an outer tube 43, an upper chamber 45, apump piston 46, and a lower chamber 47. The suction tube 41 is connectedto the mover 31 of the linear motor 30 for synchronous up/down movementwith the mover 31 and for transportation of the fluid upward through thecenter tube 34.

Referring to FIG. 3 again, an upper sleeve 50 surrounds the mover 31 ofthe linear motor 30. A thermoconducting sleeve 60 surrounds the stator32. A lower sleeve 70 is axially connected to the bottom end of thethermoconducting sleeve 60. The space defined between the upper sleeve50 and the mover 31 is filled with a thermal grease W. A stabilizer ring51 is set between the upper sleeve 50 and the mover 31 to stabilizeaxial movement of the mover 31. The thermoconducting sleeve 60 isaxially connected to the bottom end of the upper sleeve 50. Thethermoconducting sleeve 60 surrounds the stator 32 in a concentricmanner. The space defined between the thermoconducting sleeve 60 and thestator 32 is filled with a thermal grease W. The bottom end of thethermoconducting sleeve 60 is axially connected to the top end of thelower sleeve 70. The lower sleeve 70 surrounds the outer tube 43. Thespace defined between the lower sleeve 70 and the outer tube 43 isfilled with a thermal grease W. A piston 71 and multiple valve sets eachcomprised of a downward one-way valve 72 and an upward one-way valve 73are mounted in the space defined between the lower sleeve 70 and theouter tube 43. The upper sleeve 50 and the top end of the lower sleeve70 stabilize axial movement of the mover 31 and the suction tube 41. Thethermal grease W in the thermoconducting sleeve 60 dissipates heat fromthe stator 32 rapidly. The piston 71 and the multiple valve sets ofdownward one-way valves 72 and upward one-way valves 73 in the lowersleeve 70 control the space volume inside the thermoconducting sleeve 60subject to the volume change of thermal grease W in the thermoconductingsleeve 60 that expands when hot and contracts when cold.

Referring to FIG. 3 again, when the mover 31 moves downwards, thesuction tube 41 and the pump piston 46 are moved downwards by the mover31, and the one-way valve, referenced by 42, is opened, and the fluid Lin the oil well is pumped upwards from the oil well through the uppercrude oil inlet, referenced by 44, into the upper chamber 45, and at thesame time the fluid L in the lower chamber 47 is forced upwards to thesuction tube 41 and then the center tube 34 to the top oil pipe,referenced by 81, which goes up to the ground surface.

Referring to FIG. 4, when the mover 31 moves upwards, the suction tube41 and the pump piston 46 are moved upwards by the mover 31, and theone-way valve in the upper crude oil inlet 44 is closed, and thereforethe fluid L in the upper chamber 45 is forced upwards through thesuction tube 41 and then the center tube 34 to the top oil pipe,referenced by 81, which goes up to the ground surface. At the same time,the fluid L in the oil well is pumped upwards through the bottom oilpipe 82 into the lower chamber 47 via the lower crude oil inlet,referenced by 48.

Referring to FIGS. 3 and 4 again, the upper sleeve 50 and the mover 31are arranged in a concentric manner. The stabilizer ring 51 is setbetween the upper sleeve 50 and the mover 31 to stabilize axial movementof the mover 31. The thermal grease W filled in the space definedbetween the upper sleeve 50 and the mover 31 stabilizes the mover 31 andenhances heat dissipation from the mover 31.

Referring to FIGS. 3 and 4 again, the thermoconducting sleeve 60 isaxially connected between the upper sleeve 50 and the top end of thelower sleeve 70, and surrounds the stator 32 in a concentric manner.Further, the space defined between the thermoconducting sleeve 60 andthe stator 32 and the space defined between the lower sleeve 70 and theouter tube 43 are filled with a thermal grease W. Because the linearmotor 30 is submerged in the crude oil in the oil well, it is notpossible to carry heat away from the stator 32 and mover 31 of thelinear motor 30 by means of natural air or forced air during theoperation of the linear motor 30. However, the fluid L that flowsupwards through the suction tube 41 and the center tube 34 to the topoil pipe 81 carries heat away from the mover 31 rapidly; the thermalgrease W that is filled in the space defined between thethermoconducting sleeve 60 and the stator 32 transfers heat from thestator 32 to the fluid L in the oil well outside the thermoconductingsleeve 60.

Further, as stated above, the piston 71 and the one way valve sets(there are three valve sets used in the present preferred embodiment)each comprised of a downward one-way valve 72 and an upward one-wayvalve 73 are mounted in the space that is defined between the lowersleeve 70 and the outer tube 43 and filled with the thermal grease W.The space volume between piston 71 and the one way valve set below itand the space volumes between valve sets form buffer chambers. The valvesets are strong enough to sustain the weight of the thermal grease Winside the buffer chamber. During operation of the linear motor 30, heatis dissipated from the stator 32 into the thermal grease W, and thetemperature of the thermal grease W is relatively increased. Whengetting hot, the thermal grease W expands to force the piston 71downwards. As a result, the space volume of the buffer chamber belowpiston 71 is reduced and part of the thermal grease W therein isconsecutively forced through downward one-way valve 72 into the lowerbuffer chambers and eventually into the bottom oil pipe 82. When thespeed of the linear motor 30 is reduced or when the linear motor 30 isstopped, the temperature of the thermal grease W is relatively reduced.When getting cold, the thermal grease W contracts, causing the piston 71to move upwards, and therefore the thermal grease W flows backwards fromthe bottom oil pipe 82 into the lower sleeve 70 and from the lowersleeve 70 into the thermoconducting sleeve 60, i.e., the volume insidethe thermoconducting sleeve 60 is automatically adjusted to fit thevolume of the thermal grease W that expands when hot and contracts whencold.

Further, when the thermal grease W flows back upwards some of the fluidL will get into the lowest buffer chamber. The thermal grease W has aspecific gravity smaller than that of the fluid L in the oil well, sothat the fluid L entering the lowest buffer chamber from the bottom oilpipe 82 during contraction of the thermal grease W will stay at thebottom of the lowest buffer chamber avoiding mixing of the fluid L withthe thermal grease W.

In conclusion, the invention has the following features and advantages:

1. Enhancing Stabilization of the Operation:

As illustrated in FIGS. 3 and 4, the upper sleeve 50 and the lowersleeve 70 surround the mover 31 and the pump 40, supporting stable axialmovement of the mover 31 and the suction tube 41, and therefore themover 31 does not wear quickly with use due to off axial motion.

2. Better Heat Dissipation Performance:

As shown in FIGS. 3 and 4, during operation of the motor 30 and the pump40, the thermal grease W in the upper sleeve 50 stabilize reciprocatingmovement of the mover 31; the thermal grease W in thermoconductingsleeve 60 and the thermoconducting sleeve 60 transfer heat from thestator 32 to the outside fluid L in the oil well. The piston 71 andone-way valves sets each of which is comprised of an upward one-wayvalve 73 and a downward one-way valve 72 divide the space between thelower sleeve 70 and the outer tube 43 into multiple buffer chambers sothat the volume of the thermoconducting sleeve 60 is automaticallyadjusted subject to the expansion and contraction of the thermal greaseW during change of temperature.

Although a particular embodiment of the invention has been described indetail for purposes of illustration, various modifications andenhancements may be made without departing from the spirit and scope ofthe invention. Accordingly, the invention is not to be limited except asby the appended claims.

1. A mover stabilizing and stator cooling arrangement used in a 3-phaselinear motor of a submersible oil pump of a crude oil production system,said linear motor being comprised of a mover, a stator and a casing,said mover comprising a center tube and being movable up and down insaid stator, said pump being comprised of a suction tube, an outer tube,an upper chamber, a pump piston and a lower chamber, said suction tubebeing connected to said mover for synchronous up/down movement for fluidtransportation upward through center tube of the mover, moverstabilizing and stator cooling arrangement comprising an upper sleeveconcentrically surrounding said mover of said linear motor; a lowersleeve; a thermoconducting sleeve concentrically surrounding said statorand axially connected between said upper sleeve and said lower sleeve; athermal grease filled in the space defined between said upper sleeve andsaid mover and the space defined between said thermoconducting sleeveand said stator and the space defined between said lower sleeve and saidouter tube; a stabilizer ring set between said upper sleeve and saidmover to stabilize axial movement of said mover, and a piston andmultiple valve sets mounted in the space defined between said lowersleeve and said outer tube, each said valve set comprised of a downwardone-way valve and an upward one-way valve.